This invention relates to local area networks and particularly to connections between nodes in bus-type local area networks. When signals are transmitted in a local area network (LAN) certain problems arise due to imperfect electrical termination of the wire medium used for transmitting the signals. In particular, data errors may result from signal reflections caused by a mismatch between the characteristic impedance of the wire communications medium and the impedance at the ends of the network. In order to overcome this problem, the ends of the network must be terminated properly in an impedance which matches the characteristic impedance of the medium. Proper termination may be accomplished by inserting a resistive impedance load having the same impedance as the characteristic impedance of the transmission wire at each end of the network. When this resistive load is driven by a reference voltage, it matches the characteristic impedance of the transmission wire, thus effectively removing reflections which may cause data loss. For example, if a transmission cable is used which has an impedance of 100 .OMEGA., then a 100 .OMEGA. termination resistor may be inserted at the ends of the cable.
A problem arises where an end of a LAN is moved due to the connection of another device to the chain of devices which form the network. A common way that this problem has previously been overcome has been the manual placement of a terminator cap on the end of the chain following the last device. This adds extra costs and the possibility for damage or error due to the need to manually identify the end of the chain. Moreover, the terminator caps may be inadvertently removed or disconnected, threatening the performance of the entire LAN.
What is needed is a mechanism for eliminating the source of potential failure in a LAN connected through a wire medium.